The present invention relates in general to electrostatic precipitators (ESPt's) and, in particular, to a new and useful discharge electrode arrangement which facilitates field replacement of discharge electrode wires used in electrostatic precipitators.
Since the late 1800's, electrostatic precipitators have been used to remove particulates from smoke and industrial emissions. Electrostatic precipitators are widely used as an important device for combating air pollution. Electrostatic precipitators have proved to be versatile particulate collection devices and are designed for collection of solid particulates, such as fly ash, fluid-bed catalyst fines, or cement kiln dust.
Electrostatic precipitators use a discharge electrode (emitter) which can be comprised of several different constructions. The most commonly used constructions are weighted wire, rigid frame and rigid discharge electrodes. Collecting plates are aligned between the discharge electrodes in rows to form a series of parallel gas flow channels. This invention pertains to the field replacement of broken or damaged wires in a electrostatic precipitator using the rigid frame construction. With the rigid discharge frame, wires are suspended between tubes that make a rectangular frame that hangs between the rows of collecting electrode plates. Voltage is applied to the discharge electrode wires suspended in the gas flow path.
The discharge electrode wires can be configured in various ways within the discharge frame. The high potential on the discharge electrode wires causes a corona discharge, from which electrons migrate out into the gas. These create gas ions, which attach themselves to the particulates in the gas and give the particulates a charge. The collecting electrodes or collector plates are grounded so that high potential difference between them and the discharge electrodes creates a powerful electric field through which the gas must flow. This field exerts a force on the charge particles in the field such that the force moves the particles perpendicular to the gas stream to the collecting electrodes. Typically, the force on a particle 0.5 micrometers in diameter is several thousand times the force of gravity on such a particle.
Because the collector plates are grounded, the particulates lose their charge. The particulates accumulate and can be washed off of the collector plates or dislodged by mechanical agitation of the plates.
Because the spacing is very close within the discharge frames and collector plates, typically varying between 4-1/2" and 8" center to center, it is very difficult to replace the electrode discharge wires. Normally, the discharge frame arrangement with wires is prefabricated or attached during manufacture. Currently, if any discharge electrode wires become loose or broken, they are typically just removed. If replacement is desired the roof casing of the precipitator must be dismantled in order to gain access to the damaged discharge wires. At present, there is no known discharge frame and discharge electrode wire arrangement that allows for the easy maintenance of damaged discharge electrode wires.